And we know that Rasoolullaah Sallallaahu `Alayhi Wa Sallam moved his lips when reciting in both the audible and inaudible Salaah, the audible needs no explanation as you cannot recite for people to hear you if you are not moving your lips.

As for the inaudible, then one of the Sahaabah `Radhiallaahu `Anhum narrates and says: “The recitation of Nabi Sallallaahu `Alayhi Wa Sallam could be recognised in Dhuhr by the movement of his beard.” – Reported in the Musnad of Imaam Ahmad Rahimahullaah. [ii]

Meaning that they could see Rasoolullaah Sallallaahu `Alayhi Wa Sallam’s beard moving as he Sallallaahu `Alayhi Wa Sallam was reciting, while if a person were to recite in his mind without moving his lips then his beard would not move.

Fiqh:

Imaam Al-Kaasaanee Rahimahullaah says in Badaa’i`us Sanaa’i`: “A person who performs Salaah on his own and recites softly enough for his ears to hear him then it is permissible without any difference of opinion because of the certainty of the existence of recitation, because hearing without any recitation is unimaginable.

As for the case of a person who recites while pronouncing the letters correctly with his tongue but his ears does not hear it, however he has the knowledge of the fact that his tongue had moved and the letters had come out from its Makhaarij, is his Salaah valid?

There is some difference of opinion on that point; Imaam Al-Karkhi Rahimahullaah said it’s valid.”[iii]

He continues and says: “The point of Imaam Al-Karkhi Rahimahullaah is that Qiraa’ah (recitation) is an action of the tongue which is a collection of words strung together in a specific way, and that has been found (here).”[iv]

So from all this we come to understand that Qiraa’ah, recitation, is an action of the tongue and lips, and not merely reading in one’s mind, therefore we say for the validity of a person’s Salaah it is necessary that a person physically moves his tongue and lips, and he should recite at the level where he can at least hear himself, though if he recites and is not able to hear himself then too his Salaah will still be valid.